Cryogenic medium storage and reliquefaction system

Abstract

The present invention provides a cryogenic medium storage and reliquefaction system, comprising a first storage tank for selectively storing a first cryogenic medium or a second cryogenic medium, a second storage tank for storing the second cryogenic medium, a first reliquefaction unit for reliquefying flash vapor from the first storage tank, and a second reliquefaction unit for reliquefying flash vapor from the second storage tank. The boiling point of the first cryogenic medium is lower than that of the second cryogenic medium. The first reliquefaction unit comprises a compressor inlet heater, a first compressor unit, a first condenser, and a first subcooling module. The cold fluid channel of the heater is respectively connected to the outlet of the first storage tank and the inlet of the first compressor unit. The hot fluid channel of the heater is respectively connected to the outlet of the first compressor unit and the inlet of the hot fluid channel of the first condenser. The second reliquefaction unit is connected to the cold fluid channel of the first condenser to provide liquid second cryogenic medium to the first condenser. The present invention saves equipment cost and space.

Description

Technical Field

[0001] The present invention relates to the technical field of cryogenic medium storage, and in particular to a cryogenic medium storage and reliquefaction system. Background Art

[0002] Propane is a byproduct of natural gas, associated gas from oilfields, and crude oil refining. During the crude oil refining process, propane production cannot be easily adjusted to meet demand. Propane is a key component of LPG (liquefied petroleum gas). With the growing application of LPG in the chemical industry, future growth in LPG demand is expected to outpace supply growth.

[0003] Over 95% of the world's ethane comes from crude oil or natural gas processing, with less than 5% coming from light hydrocarbons in refineries. Due to transportation difficulties, ethane trade is currently limited to intra-regional pipelines, with intercontinental trade being rare. Furthermore, ethane storage costs are high, and while some inventory exists, it's small.

[0004] For ease of storage, ethane and propane are stored in liquid form in tanks. The storage temperature for liquid ethane is approximately -91°C, and the storage temperature for liquid propane is approximately -41°C. Flash gas (BOG) is inevitably generated due to heat leakage through tank walls and piping, as well as drops in atmospheric pressure.

[0005] To avoid waste, storage facilities are equipped with reliquefaction equipment to compress and recondense the BOG produced in the tanks for recovery. For facilities that need to store both ethane and propane, the need for reliquefaction equipment increases, requiring significant floor space and resulting in high costs. Summary of the Invention

[0006] The object of the present invention is to provide a cryogenic medium storage and reliquefaction system to solve the problem of high system cost when storing multiple cryogenic media in the prior art.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: a low-temperature medium storage and reliquefaction system, comprising a first storage tank, a second storage tank, a first reliquefaction unit and a second reliquefaction unit; the first storage tank is used to selectively store a first low-temperature medium or a second low-temperature medium; wherein the boiling point of the first low-temperature medium is lower than the boiling point of the second low-temperature medium; the design temperature of the first storage tank is lower than the boiling point of the first low-temperature medium; the second storage tank is used to store the second low-temperature medium; the first reliquefaction unit comprises a compressor inlet heater, a first compressor group, a first condenser, and a first subcooling module; the compressor inlet heater and the first condenser both have a cold fluid channel and a hot fluid channel for mutual heat exchange; the cold fluid channel of the compressor inlet heater is connected to the outlet of the first storage tank and the inlet of the first compressor group, respectively; the compressor The hot fluid channel of the machine inlet heater is respectively connected to the outlet of the first compressor unit and the inlet of the hot fluid channel of the first condenser; the first subcooling module is connected to the outlet of the hot fluid channel of the first condenser for subcooling the liquid low-temperature medium; the second reliquefaction unit is connected to the second storage tank for reliquefying the flash gas in the second storage tank into a liquid second low-temperature medium; the second reliquefaction unit is also connected to the cold fluid channel of the first condenser to provide the liquid second low-temperature medium to the cold fluid channel of the first condenser; the first condenser utilizes the cold capacity of the second low-temperature medium from the second reliquefaction unit flowing through its cold fluid channel to condense the compressed flash gas from the first storage tank in its hot fluid channel, and the condensed liquid low-temperature medium enters the first subcooling module.

[0008] In one embodiment, the first subcooling module includes a first condensate collector and a first economizer; the inlet of the first condensate collector is connected to the outlet of the hot fluid channel of the first condenser; the first economizer has a first throttling device and a first heat exchange device, and the first heat exchange device has a first throttling side channel and a first subcooling side channel for mutual heat exchange; the inlet of the first throttling device and the inlet of the first subcooling side channel are both connected to the outlet of the first condensate collector; the outlet of the first throttling device is connected to the inlet of the first throttling side channel; the outlet of the first subcooling side channel outputs subcooled liquid low-temperature medium.

[0009] In one embodiment, the first compressor unit is further provided with an air supply port; the first reliquefaction unit further includes an air supply heater; the air supply heater has a cold fluid channel for a low-temperature medium to flow and absorb heat; the cold fluid channel of the air supply heater is respectively connected to the air supply port of the first compressor unit and the outlet of the first throttling side channel.

[0010] In one embodiment, the supplementary air heater further has a hot fluid channel for releasing heat to its cold fluid channel; the hot fluid channel of the supplementary air heater is connected between the outlet of the hot fluid channel of the compressor inlet heater and the inlet of the hot fluid channel of the first condenser.

[0011] In one embodiment, the second reliquefaction unit includes a second compressor group, a second condenser and a second subcooling module connected in sequence; the inlet of the second compressor group is connected to the outlet of the second storage tank; the outlet of the second subcooling module is connected to the inlet of the second storage tank and the inlet of the cold fluid channel of the first condenser.

[0012] In one embodiment, the second subcooling module includes a second condensate collector and a second economizer; the inlet of the second condensate collector is connected to the outlet of the second condenser; the second economizer has a second throttling device and a second heat exchange device, and the second heat exchange device has a second throttling side channel and a second subcooling side channel for mutual heat exchange; the inlet of the second throttling device and the inlet of the second subcooling side channel are both connected to the outlet of the second condensate collector; the outlet of the second throttling device is connected to the inlet of the second throttling side channel; the outlet of the second subcooling side channel is respectively connected to the inlet of the second storage tank and the inlet of the cold fluid channel of the first condenser.

[0013] In one embodiment, the second compressor unit is provided with an air supply port, and the air supply port of the second compressor unit is connected to the outlet of the second throttling side channel.

[0014] In one embodiment, the second condensate collector is a horizontal storage tank.

[0015] In one embodiment, the second condenser is a water-cooled heat exchanger.

[0016] In one embodiment, both the first storage tank and the second storage tank are fully contained concrete storage tanks.

[0017] As can be seen from the above technical solution, the advantages and positive effects of the present invention are as follows: In the present invention, the first storage tank is designed based on the storage requirements of the first cryogenic medium with a lower boiling point, allowing it to serve as a storage tank for both the first cryogenic medium and the second cryogenic medium, selectively switching storage according to demand. There is no need for a separate storage tank dedicated to the first cryogenic medium. This is particularly suitable for situations where the storage demand for the first cryogenic medium is low, thus reducing the system footprint. The various equipment in the first reliquefaction unit associated with the first storage tank can also be switched accordingly to achieve reliquefaction processing of different cryogenic media, improving operational flexibility, reducing equipment layout, saving equipment costs and floor space, and reducing overall investment costs. Specifically, the first reliquefaction unit is equipped with a compressor inlet heater before the first compressor unit, which can heat the BOG from the first storage tank before compressing it. When the first tank stores the first cryogenic medium, the design of the compressor inlet heater allows the first compressor unit to also be used to compress the first cryogenic medium BOG, saving equipment configuration and reducing costs.

[0018] Furthermore, in the first reliquefaction unit, the second cryogenic medium reliquefied from the second reliquefaction unit is used as a refrigerant via the first condenser to cool the BOG from the first storage tank. This eliminates the need for a separate refrigerant and its associated equipment for the first reliquefaction unit. Instead, the second reliquefaction unit, equipped with the second cryogenic medium storage system, directly supplies refrigerant to the first reliquefaction unit. This design significantly reduces equipment consumption, optimizes processes, and improves the economic efficiency of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the principle of an embodiment of the present invention.

[0020] The following are the descriptions of the reference numerals:

[0021] 1. The first storage tank;

[0022] 2. Second storage tank;

[0023] 3. First reliquefaction unit; 31. Compressor inlet heater; 311. Cold fluid channel; 312. Hot fluid channel; 32. First compressor unit; 321. Inlet; 322. Outlet; 323. Air supply port; 33. First condenser; 331. Cold fluid channel; 332. Hot fluid channel; 34. First condensate collector; 35. First economizer; 351. First throttling device; 352. First heat exchange device; 3521. First throttling side channel; 3522. First subcooling side channel; 36. Air supply heater; 361. Cold fluid channel; 361. Hot fluid channel;

[0024] 4. Second reliquefaction unit; 41. Second compressor unit; 411. Inlet; 412. Outlet; 413. Air supply port; 42. Second condenser; 43. Second condensate collector; 44. Second economizer; 441. Second throttling device; 442. Second heat exchange device; 45. Refrigerant pipeline; 451. Control valve. DETAILED DESCRIPTION

[0025] Typical embodiments embodying the features and advantages of the present invention are described in detail in the following description. It should be understood that the present invention is capable of various variations in different embodiments without departing from the scope of the present invention, and that the descriptions and illustrations herein are intended to be illustrative rather than limiting.

[0026] The present invention provides a cryogenic medium storage and reliquefaction system for storing cryogenic medium and reliquefying cryogenic medium flash vapor. The system is primarily applicable to locations such as cryogenic medium receiving stations. The system can store two different light hydrocarbon cryogenic media. These two cryogenic media are preferably of the same type with similar physical properties, such as ethane and propane, or ethylene and propylene, or other similar light hydrocarbon media.

[0027] The following is a detailed description using an example in which ethane and propane can be stored.

[0028] like Figure 1 As shown, the cryogenic medium storage and reliquefaction system of this embodiment mainly includes a first storage tank 1 , a second storage tank 2 , a first reliquefaction unit 3 and a second reliquefaction unit 4 .

[0029] The first storage tank 1 and the second storage tank 2 are preferably fully contained concrete low-temperature storage tanks with a large storage capacity. The specific structure of the tanks can be referred to in the relevant art and will not be described in detail here.

[0030] In this embodiment, the second storage tank 2 is used to store propane. It is designed according to the storage requirements of propane, and its design temperature and design pressure meet the storage requirements of propane.

[0031] First storage tank 1 is designed to accommodate ethane storage requirements, with its design temperature and design pressure meeting these requirements. For example, in one specific application, its design pressure is -5 to +29 mbarg, and its design temperature is -104°C, both lower than ethane's boiling point of -88.6°C. Because the boiling point of ethane, -88.6°C, is lower than that of propane, -42.09°C, the storage requirements for ethane are more stringent than those for propane. Therefore, first storage tank 1 can function as both an ethane or propane storage tank, selectively storing either propane or ethane based on actual needs.

[0032] It should be noted that when the cryogenic medium stored in the first storage tank 1 needs to be switched, the cryogenic medium originally stored in the first storage tank 1 must be emptied and then new cryogenic medium must be injected according to regulations.

[0033] Among them, propane and ethane are stored in corresponding storage tanks in liquid form.

[0034] The first reliquefaction unit 3 is used to reliquefy the flash gas (Boil-Off Gas, commonly referred to as BOG) in the first storage tank 1, and the second reliquefaction unit 4 is used to reliquefy the flash gas in the second storage tank 2. In this embodiment, the second reliquefaction unit 4 provides a portion of the reliquefied propane liquid to the first reliquefaction unit 3. The propane liquid serves as a refrigerant to cool the flash gas in the first reliquefaction unit 3. This utilizes the cold energy of the propane liquid, reduces reliance on external refrigerants, and improves operational economy and flexibility.

[0035] In this embodiment, the first reliquefaction unit 3 includes a compressor inlet heater 31 , a first compressor unit 32 , a first condenser 33 , a first condensate collector 34 , and a first economizer 35 , and preferably also includes a supplementary air heater 36 .

[0036] The compressor inlet heater 31 is mainly used to heat the flash gas from the first storage tank 1. When ethane is stored in the first storage tank 1, the temperature of the ethane flash gas heated by the compressor inlet heater 31 meets the inlet temperature requirement of the first compressor unit 32, so that the first compressor unit 32 can compress the ethane flash gas.

[0037] In particular, in this embodiment, the heat source for compressor inlet heater 31 is derived from ethane flash vapor compressed by first compressor unit 32, eliminating the need for an external heat source and improving operational efficiency. Specifically, compressor inlet heater 31 includes a cold fluid channel 311 and a hot fluid channel 312 for heat exchange with each other.

[0038] The inlet of the cold fluid channel 311 of the compressor inlet heater 31 is connected to the first storage tank 1 , and the outlet of the cold fluid channel 311 is connected to the inlet 321 of the first compressor unit 32 to heat the flash gas from the first storage tank 1 and then send it into the first compressor unit 32 .

[0039] The inlet of the hot fluid channel 312 of the compressor inlet heater 31 is connected to the outlet 322 of the first compressor unit 32. This allows the compressed, pressurized, and heated flash steam to heat the flash steam from the first storage tank 1, thereby cooling it. The outlet of the hot fluid channel 312 further divides into two paths: one is an external transmission pipeline, where the cooled flash steam can be transported externally as needed; the other is connected to the first condenser 33 via the air supply heater 36 for subsequent condensation processing.

[0040] The first compressor unit 32 may be a screw compressor. In this embodiment, in addition to the inlet 321 and the outlet 322 , it is further provided with an air supply port 323 .

[0041] The first condenser 33 also has a cold fluid channel 331 and a hot fluid channel 332 that exchange heat with each other.

[0042] The inlet of the cold fluid channel 331 is connected to the second reliquefaction unit 4 to receive the reliquefied propane liquid from the second reliquefaction unit 4. The outlet of the cold fluid channel 331 is connected to the BOG pipeline of propane.

[0043] The inlet of the hot fluid channel 332 is connected to the outlet of the hot fluid channel 312 of the compressor inlet heater 31 through the supplementary air heater 36 , and the outlet of the hot fluid channel 332 is connected to the inlet of the first condensate collector 34 .

[0044] The compressed flash gas from the compressor inlet heater 31 passes through the supplementary air heater 36 and then enters the first condenser 33. It is then cooled by the propane liquid from the second reliquefaction unit 4 and condensed into liquid cryogenic medium. The condensed liquid cryogenic medium enters the first condensate collector 34.

[0045] First condensate collector 34 is a small storage container, optionally in the form of a horizontal tank. The condensed liquid (i.e., liquid cryogenic medium) after condensation in first condenser 33 is collected in first condensate collector 34 and then enters first economizer 35. First condensate collector 34 acts as a buffer, allowing further processing after a certain amount of liquid has accumulated, thereby improving process efficiency.

[0046] The first economizer 35 includes a first throttling device 351 and a first heat exchange device 352. The first heat exchange device 352 has a first throttling channel 3521 and a first subcooling channel 3522, which exchange heat with each other. The inlet of the first throttling device 351 and the inlet of the first subcooling channel 3522 are both connected to the outlet of the first condensate collector 34; the outlet of the first throttling device 351 is connected to the inlet of the first throttling channel 3521; the outlet of the first subcooling channel 3522 outputs subcooled liquid cryogenic medium; and the outlet of the first throttling channel 3521 is connected to the air supply heater 36.

[0047] The first economizer 35 divides the condensed liquid from the first condensate collector 34 into two parts. One part is throttled by the first throttling device 351, further cooled by thermal expansion, and then enters the first throttling side channel 3521 of the first heat exchange device 352. The other part directly enters the first subcooling side channel 3522 of the first heat exchange device 352, cooling the condensed liquid and supercooling it. The subcooled liquid stabilized in the first subcooling side channel 3522 enters the condensate main pipe, where it can be returned to the first storage tank 1 for storage.

[0048] The first economizer 35 utilizes a portion of the medium to expand and refrigerate itself to stabilize another portion of the liquid low-temperature medium, without introducing an external refrigerant, thereby improving energy utilization and being energy-saving and environmentally friendly.

[0049] In this embodiment, the first condensate collector 34 and the first economizer 35 together constitute a first subcooling module, which subcools the liquid cryogenic medium to produce a stable, subcooled liquid cryogenic medium. This method does not require the use of an external refrigerant. In other embodiments, other heat exchange methods can be used to subcool the liquid cryogenic medium, such as using a low-temperature external refrigerant such as liquid nitrogen. However, this method is less economical than the method using the first economizer 35 in this embodiment.

[0050] The supplementary air heater 36 includes a cold fluid channel 361 and a hot fluid channel 362 that can exchange heat with each other. The hot fluid channel 362 releases heat to the cold fluid channel 361 .

[0051] The inlet of cold fluid channel 361 is connected to the outlet of first throttling channel 3521, and the outlet of cold fluid channel 361 is connected to the gas supply port 323 of first compressor unit 32. This allows the low-temperature gaseous medium, which has absorbed heat and evaporated in first throttling channel 3521, to be heated and fed into first compressor unit 32 for further use, thereby improving the utilization rate of the low-temperature medium. The low-temperature ethane gas absorbs heat while flowing in cold fluid channel 361, raising its temperature to meet the inlet temperature requirement of first compressor unit 32.

[0052] The heated heat medium comes from the ethane gas compressed by the first compressor unit 32 in the compressor inlet heater 31. Specifically, the inlet of the hot fluid channel 362 is connected to the outlet of the hot fluid channel 312 of the compressor inlet heater 31, and the outlet of the hot fluid channel 362 is connected to the inlet of the hot fluid channel 332 of the first condenser 33.

[0053] The first reliquefaction unit 3 is also provided with some auxiliary function sensors, regulating valves and other equipment, which can be set in some corresponding pipelines according to actual needs. This is not the focus of this embodiment and will not be described in detail.

[0054] Second reliquefaction unit 4 is configured based on the reliquefaction requirements of propane stored in second storage tank 2. In this embodiment, second reliquefaction unit 4 primarily comprises a second compressor unit 41, a second condenser 42, a second condensate collector 43, and a second economizer 44. Each component is selected to meet propane requirements.

[0055] The inlet 411 of the second compressor unit 41 is connected to the second storage tank 2, and the outlet 412 of the second compressor unit 41 is connected to the second condenser. The second compressor unit 41 compresses the propane flash vapor in the second storage tank 2, thereby increasing the pressure and temperature of the propane flash vapor. The second compressor unit 41 can also be a screw compressor.

[0056] The second condenser 42 of this embodiment is a water-cooled heat exchanger, which may optionally adopt a shell-and-tube structure. The second condenser 42 cools the propane flash vapor flowing through the second condenser 42 using external cooling water, thereby reducing the temperature of the propane flash vapor and condensing it into propane liquid, while the pressure remains essentially unchanged. The cooling water flows through the tube side of the second condenser 42, absorbing the heat of the propane flash vapor in the shell side of the second condenser 42 and condensing the propane flash vapor. By adjusting the flow rate of the cooling water, the cooling rate can be controlled, and the outlet pressure of the second compressor unit 41 can be set accordingly. In other embodiments, the structure of the second condenser 42 can be adjusted according to actual conditions, and the cooling water can also be selected from other cooling media according to actual conditions.

[0057] Second condensate collector 43 is a small storage container, optionally in the form of a horizontal tank. The condensed propane liquid is collected in second condensate collector 43 and then enters second economizer 44. Similarly, second condensate collector 43 acts as a buffer for the propane liquid, allowing it to accumulate to a certain amount before proceeding to the next step of processing, thereby improving the economic efficiency of the process.

[0058] The structure of the second economizer 44 is the same as that of the first economizer 35. The second economizer 44 has a second throttling device 441 and a second heat exchange device 442, and the second heat exchange device 442 has a second throttling side channel (not numbered in the figure) and a second subcooling side channel (not numbered in the figure) for mutual heat exchange; the inlet of the second throttling device 441 and the inlet of the second subcooling side channel are both connected to the outlet of the second condensate collector 43; the outlet of the second throttling device 441 is connected to the inlet of the second throttling side channel, and the outlet of the second throttling side channel then enters the air supply port 413 of the second compressor unit 41 for continued use.

[0059] In the second economizer 44, a portion of the propane liquid is throttled and expanded, cooling the remaining portion to subcool it. The outlet of the second subcooling channel outputs stable subcooled propane liquid, which is then split into two paths: one path connects to the inlet of the second storage tank 2, where the propane liquid returns to the second storage tank 2; the other path connects via refrigerant pipe 45 to the inlet of the cold fluid channel 331 of the first condenser 33, thereby supplying propane liquid as refrigerant to the first reliquefaction unit 3. A control valve 451 is provided on the refrigerant pipe 45 to control the flow of the refrigerant.

[0060] Based on the above introduction, an application example is further introduced below.

[0061] The above-mentioned cryogenic medium storage and reliquefaction system is used in an ethane / propane storage and supporting engineering project. In this project, the pressure of propane BOG exported from the propane storage tank is 0.1 barg, the temperature is -35.1°C, and the processing capacity is 8350 kg / h; the pressure of ethane BOG exported from the ethane storage tank is 0.176 barg, the temperature is -73.3°C, and the processing capacity is 3154 kg / h.

[0062] The molar composition of propane BOG is:

[0063]

[0064]

[0065] The molar composition of ethane BOG is:

[0066] Components Percentage (mole%) Ethane 83.93 methane 15.78 Propane 0.29

[0067] When the first storage tank 1 stores ethane and the second storage tank 2 stores propane, the workflow of the above reliquefaction process is roughly as follows.

[0068] 1. Propane reliquefaction process:

[0069] Propane BOG gas at 0.1 barg and -35.1°C in second storage tank 2 enters second compressor unit 41 at a flow rate of 8350 kg / h, where it is pressurized and heated to 78°C and 18.59 barg. The pressurized and heated propane gas is condensed by cooling water in the shell side of second condenser 42. The condensed propane liquid is collected in second condensate collector 43; at this point, the propane liquid has a pressure of 18.58 barg and a temperature of 43°C. The propane liquid in the second condensate collector 43 then enters the downstream second economizer 44, and part of the condensate will be flashed to an intermediate pressure of 1.28 barg (-19.8°C) in the second throttling device 441 of the second economizer 44; the flashed condensate will be cooled to -33°C, 1.01 barg in the second subcooling side channel of the second heat exchange device 442 of the second economizer 44; the gas produced by the flashing will then enter the air supply port 413 of the second compressor unit 41; part of the subcooled propane liquid will return to the second storage tank 2, and the other part can be used as a refrigerant for ethane condensation.

[0070] 2. Ethane reliquefaction process:

[0071] Ethane BOG gas at 0.176 barg and -73.3°C in the first storage tank 1 enters the compressor inlet heater 31 at a flow rate of 3157 kg / h, heated to -40°C and 0.156 barg, before entering the first compressor unit 32. The heat medium in the compressor inlet heater 31 is the ethane BOG gas (85°C and 18.337 barg) compressed by the first compressor unit 32. The compressed ethane BOG gas cools down to 63.7°C and 17.837 barg after passing through the compressor inlet heater 31. It then enters the make-up heater 36, preheating the ethane gas entering the make-up port 323 of the first compressor unit 32. The gas then enters the first condenser 33, where it is condensed by propane liquid (0.4 barg and -42.5°C) from the second reliquefaction unit 4. The propane liquid evaporates in the first condenser 33 to 0.3 barg and -38.3°C before entering the propane BOG pipeline. The condensed ethane is collected in the first condensate collector 34 and then enters the downstream first economizer 35. A small portion of the ethane condensate will be flashed to an intermediate pressure of 1.8 barg, -69.6°C in the first economizer 35. The majority of the condensate is cooled to a subcooled state (16.337 barg, -71.9°C) in the first economizer 35. The subcooled ethane liquid is sent to the first storage tank 1. The ethane gas flashed in the first economizer 53 enters the air supply heater 36 and returns to the air supply port 323 of the first compressor unit 32 after preheating.

[0072] Based on the concept of the present invention, when the cryogenic medium stored in the cryogenic medium storage and reliquefaction system is ethylene and propylene, since the boiling point of ethylene is lower than that of propylene, accordingly, the first storage tank 1 is used to store ethylene or propylene, and the second storage tank 2 is used to store propylene.

[0073] According to the above introduction, the present invention has the following advantages:

[0074] In the present invention, the first storage tank is designed to store the first cryogenic medium with a lower boiling point, allowing it to serve as both the first and second cryogenic mediums, selectively switching between them based on demand. This eliminates the need for a separate, dedicated storage tank for the first cryogenic medium, making it particularly suitable for situations where the storage demand for the first cryogenic medium is low, thereby reducing the system's footprint. The various devices in the first reliquefaction unit associated with the first storage tank can also be switched accordingly, enabling reliquefaction of different cryogenic media. This improves operational flexibility, reduces equipment layout, saves equipment costs and floor space, and reduces overall investment costs, ultimately lowering the cost of cryogenic medium storage.

[0075] The first reliquefaction unit is equipped with a compressor inlet heater before the inlet of the first compressor unit. This heater can heat the BOG from the first storage tank before compressing it. When the first storage tank stores the first cryogenic medium, the BOG temperature of the heated first cryogenic medium can meet the inlet temperature requirement of the first compressor unit, allowing the first compressor unit to compress both cryogenic media and BOG, saving equipment investment. Similarly, a supplementary air heater is equipped before the supplementary air port of the first compressor unit, ensuring that the BOG temperature of the first cryogenic medium entering the supplementary air port of the first compressor unit also meets the inlet temperature requirement of the first compressor unit. Through the configuration of this compressor inlet heater and supplementary air heater, the first compressor unit, whose design temperature is only suitable for the second cryogenic medium with a higher boiling point, can also be used to compress the first cryogenic medium with a lower boiling point, saving investment in compressor unit equipment and reducing costs.

[0076] Furthermore, in the first reliquefaction unit, by using the second reliquefaction unit equipped for the second storage tank as the refrigerant compression circulation device of the first reliquefaction unit, the BOG in the first storage tank is cooled using the reliquefied second low-temperature medium as the refrigerant. This eliminates the need to configure a separate refrigerant compression circulation device for the first reliquefaction unit, thereby saving equipment costs and improving the operational flexibility of the device.

[0077] Furthermore, in both the first reliquefaction unit and the second reliquefaction unit, economizers are used as heat exchangers for supercooling treatment, utilizing the expansion and refrigeration of a portion of the cryogenic medium itself to stabilize another portion of the cryogenic medium, thereby obtaining a stable liquid cryogenic medium without the need to introduce external refrigerant, thereby improving economy, and increasing system capacity and efficiency.

[0078] The system of the present invention has a wide range of applications and is not only applicable to ethane / propane, but also to light hydrocarbon compounds such as ethylene / propylene, and has great design flexibility.

[0079] While the present invention has been described with reference to several exemplary embodiments, it should be understood that the terms used are intended to be illustrative and exemplary rather than restrictive. Since the present invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above-described embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope of the appended claims. All changes and modifications that fall within the scope of the claims or their equivalents are intended to be covered by the appended claims.

Claims

1. A cryogenic medium storage and reliquefaction system, characterized in that: include: a first storage tank for selectively storing a first cryogenic medium or a second cryogenic medium; wherein the boiling point of the first cryogenic medium is lower than the boiling point of the second cryogenic medium; and a design temperature of the first storage tank is lower than the boiling point of the first cryogenic medium; a second storage tank, for storing a second cryogenic medium; The first reliquefaction unit includes a compressor inlet heater, a first compressor unit, a first condenser, and a first subcooling module; the compressor inlet heater and the first condenser each have a cold fluid channel and a hot fluid channel for heat exchange with each other; the cold fluid channel of the compressor inlet heater is respectively connected to the outlet of the first storage tank and the inlet of the first compressor unit; the hot fluid channel of the compressor inlet heater is respectively connected to the outlet of the first compressor unit and the inlet of the hot fluid channel of the first condenser; the first subcooling module is connected to the outlet of the hot fluid channel of the first condenser for subcooling the liquid cryogenic medium; a second reliquefaction unit, connected to the second storage tank, for reliquefying the flash gas in the second storage tank into a liquid second cryogenic medium; the second reliquefaction unit is also connected to the cold fluid channel of the first condenser to provide the liquid second cryogenic medium to the cold fluid channel of the first condenser; The first condenser utilizes the cold energy of the second cryogenic medium from the second reliquefaction unit flowing through its cold fluid channel to condense the compressed flash gas from the first storage tank in its hot fluid channel, and the condensed liquid cryogenic medium enters the first subcooling module.

2. The cryogenic medium storage and reliquefaction system according to claim 1, characterized in that: The first subcooling module includes a first condensate collector and a first economizer; The inlet of the first condensate collector is connected to the outlet of the hot fluid channel of the first condenser; The first economizer comprises a first throttling device and a first heat exchange device, wherein the first heat exchange device comprises a first throttling side channel and a first subcooling side channel for heat exchange with each other; the inlet of the first throttling device and the inlet of the first subcooling side channel are both connected to the outlet of the first condensate collector; the outlet of the first throttling device is connected to the inlet of the first throttling side channel; The outlet of the first subcooling side channel outputs the subcooled liquid cryogenic medium.

3. The cryogenic medium storage and reliquefaction system according to claim 2, characterized in that: The first compressor unit is further provided with an air supply port; the first reliquefaction unit further comprises an air supply heater; The air supply heater has a cold fluid channel for low-temperature medium to flow and absorb heat; the cold fluid channel of the air supply heater is respectively connected to the air supply port of the first compressor unit and the outlet of the first throttling side channel.

4. The cryogenic medium storage and reliquefaction system according to claim 3, characterized in that: The supplementary air heater also has a hot fluid channel for releasing heat to its cold fluid channel; the hot fluid channel of the supplementary air heater is connected between the outlet of the hot fluid channel of the compressor inlet heater and the inlet of the hot fluid channel of the first condenser.

5. The cryogenic medium storage and reliquefaction system according to any one of claims 1 to 4, characterized in that: The second reliquefaction unit includes a second compressor group, a second condenser and a second subcooling module connected in sequence; the inlet of the second compressor group is connected to the outlet of the second storage tank; the outlet of the second subcooling module is connected to the inlet of the second storage tank and the inlet of the cold fluid channel of the first condenser.

6. The cryogenic medium storage and reliquefaction system according to claim 5, characterized in that: The second subcooling module includes a second condensate collector and a second economizer; The inlet of the second condensate collector is connected to the outlet of the second condenser; The second economizer has a second throttling device and a second heat exchange device, and the second heat exchange device has a second throttling side channel and a second subcooling side channel for mutual heat exchange; the inlet of the second throttling device and the inlet of the second subcooling side channel are both connected to the outlet of the second condensate collector; the outlet of the second throttling device is connected to the inlet of the second throttling side channel; the outlet of the second subcooling side channel is respectively connected to the inlet of the second storage tank and the inlet of the cold fluid channel of the first condenser.

7. The cryogenic medium storage and reliquefaction system according to claim 6, characterized in that: The second compressor unit is provided with an air supply port, and the air supply port of the second compressor unit is connected to the outlet of the second throttling side channel.

8. The cryogenic medium storage and reliquefaction system according to claim 6, characterized in that: The second condensate collector is a horizontal storage tank.

9. The cryogenic medium storage and reliquefaction system according to claim 5, characterized in that: The second condenser is a water-cooled heat exchanger.

10. The cryogenic medium storage and reliquefaction system according to claim 1, characterized in that: The first storage tank and the second storage tank are both fully contained concrete storage tanks.

Images